WASHINGTON (Reuters) - U.S. President Donald Trump has instructed aides to proceed with tariffs on about $200 billion more Chinese goods, despite Treasury Secretary Steven Mnuchin's attempts to restart trade talks with China, a source familiar with the decision said.

But the timing for activating the additional tariffs was unclear, the person said.

The green light for the tariffs, first reported by Bloomberg, had an immediate effect on financial markets. It led U.S. stocks to trade lower, fuelled drops in the Chinese yuan in offshore trading and gains in the dollar index , and sent the S&P 500 index negative.

The decision comes one week after Trump said he would be adding tariffs on $200 billion in Chinese goods and had tariffs on another $267 billion in Chinese imports "ready to go on short notice if I want."

A public comment period also ended last week for the $200 billion tariff list, which would hit various internet technology products and other electronics, printed circuit boards and consumer goods ranging from handbags to bicycles and furniture.

The U.S. Trade Representative's office has said it was working to revise the list based on issues raised in public hearings and written submissions. In previous rounds of anti-China tariffs, it has taken one to two weeks to revise the list and another two to three weeks to begin collecting tariffs.

The decision also comes despite a Treasury invitation earlier this week to senior Chinese officials, including Vice Premier Liu He, for more talks to try to resolve trade differences between the world's two largest economies.

China's foreign ministry said it welcomed the invitation, but Trump later raised questions about it, saying on Twitter that he was under no pressure to make a deal with Beijing and that the United States "will soon be taking in Billions in Tariffs & making products at home. If we meet, we meet?"

A Treasury spokesman did not immediately respond to a query on the status of the China talks invitation. A USTR spokesman did not respond to queries about the tariffs.

Trump has already levied duties on $50 billion worth of Chinese goods based on his demands that China reduce its $375 billion trade surplus with the United States and make sweeping changes to policies on intellectual property and technology transfers and roll back high tech industrial subsidies.

The tariffs on the $50 billion of goods already imposed, the $200 billion list and another $267 billion of Chinese goods would exceed the $505 billion in goods that the United States imported from China last year. But 2018 imports from China through July were up nearly 9 percent over the same period of 2017, according to U.S. Census Bureau data.

(Additional reporting by Lisa Lambert and David Lawder; Editing by Chizu Nomiyama and Phil Berlowitz)

This story has not been edited by Firstpost staff and is generated by auto-feed.